Lithium battery structures

ABSTRACT

This invention provides a novel battery structure that, in some variations, utilizes a mixed lithium-ion and electron conductor as part of the separator. This layer is non-porous, conducting only lithium ions during operation, and may be structurally free-standing. Alternatively, the layer can be used as a battery electrode in a lithium-ion battery, wherein on the side not exposed to battery electrolyte, a chemical compound is used to regenerate the discharged electrode. This battery structure overcomes critical shortcomings of current lithium-sulfur, lithium-air, and lithium-ion batteries.

PRIORITY DATA

This patent application is a divisional application of U.S. Pat. No.8,623,556, issued on Jan. 7, 2014, which is a divisional of U.S. Pat.No. 8,481,195, issued on Jul. 9, 2013, both of which are herebyincorporated by reference herein.

FIELD OF THE INVENTION

The present invention generally relates to improved battery structures,such as lithium-ion, lithium-sulfur, and lithium-air batteries.

BACKGROUND OF THE INVENTION

Batteries based on lithium (Li), such as lithium-ion batteries, areattractive due to their high energy density compared to other commercialbatteries. Lithium-ion batteries are used commercially today incomputers, cell phones, and related devices.

Lithium-based batteries (including lithium-ion, lithium-sulfur, andlithium-air systems) have significant potential in transportationapplications, such as electric vehicles. For transportation-relatedapplications, long cycle life is a requirement. Presently, thisrequirement has not been met.

Battery lifetime is often a critical factor in the marketplace,especially for commercial, military, and aerospace applications.Previous methods of extending battery life include employing long-lifecathode and anode materials, and restricting battery operation to avoidconditions detrimental to battery life. Examples of such detrimentalconditions include high and low temperatures, high depths of discharge,and high rates. These restrictions invariably lead to under-utilizationof the battery, thus lowering its effective energy density. In addition,precise control of cell temperature with aggressive thermal managementon the pack level is usually required, which adds significantly tosystem weight, volume, and cost.

A problem in the art associated with lithium-sulfur, lithium-air, andlithium-ion batteries is undesirable chemical migration that results inparasitic chemical reactions at the anode or cathode. For example, inbatteries with manganese oxide and iron phosphate cathodes, dissolvedmetal ions often migrate to the anode where they are reduced andcompromise the integrity of the solid electrolyte interface layer.Battery capacity degrades due to consumption of active ions. Batterystorage and cycle life can be greatly improved if such undesirablechemical interactions are reduced or eliminated.

A successful battery separator layer should have a wide electrochemicalstability window to be stable against the battery anode and cathode. Inaddition, the separator layer needs to have limited electronicconductivity in order to prevent electrical leakage between the twoelectrodes. When both requirements are imposed, the available materialsare very limited and solid electrolyte is rarely free-standing.

In view of the foregoing shortcomings, new battery structures are neededto address important commercialization issues associated withlithium-sulfur, lithium-air, and lithium-ion batteries. For example, arelatively thin free-standing separator layer is a long-felt need in theart. Preferred battery structures would help prevent or eliminatebattery failure due to eventual contamination during operation, therebyincreasing battery lifetime and overall energy efficiency.

SUMMARY OF THE INVENTION

The present invention addresses the aforementioned needs in the art, aswill now be summarized and further described in detail herein.

In some variations, this invention provides a battery structurecomprising:

(a) an anode for extracting selected metal ions (such as lithium ions);

(b) a cathode for inserting the metal ions;

(c) an electrolyte for transporting the metal ions between the anode andthe cathode; and

(d) a separator comprising a non-porous layer that is electronicallyconductive and permeable to the metal ions but not appreciably permeableto any other chemical species.

The non-porous layer is a mixed ion and electron conductor with variousionic and electronic conductivities. In some embodiments, the ionicconductivity of the metal ions in the non-porous layer is selected fromabout 10⁻⁵ to 10⁻² S/cm, such as about 10⁻³ to 10⁻² S/cm. In someembodiments, the electronic conductivity of electrons in the non-porouslayer is selected from about 10⁻² to 10⁻² S/cm, such as about 10⁻¹ to 1S/cm.

The non-porous layer may have a thickness selected from about 2 to 200μm, for example. In some embodiments, the non-porous layer is afree-standing layer without structural support by either of the anode orthe cathode.

In some embodiments, the non-porous layer comprises lithium metal oxide,lithium metal phosphate, or lithium metal sulfide. The non-porous layermay have a composition that is the same as, or different from, thecomposition of either of the anode or the cathode.

In various embodiments, the non-porous layer comprises one or morecompositions selected from the group consisting of Li_(x)Mn₂O₄ (0<x<2),Li_(x)CoO₂ (0<x<1), Li_(x)NiO₂ (0<x<1), Li_(x)V₂O_(y) (0<x<5, 4<y<5),Li_(x)TiO₂ (0<x<1), Li₄₊₁Ti₅O₁₂ (0<x<3), Li_(x)WO₃ (0<x<0.5),Li_(x)Nb₂O₅ (0<x<3), Li_(x)TiS₂ (0<x<1), Li_(x)MPO₄ (M=Mn, Fe, and/or V;0<x<1), and LiMPO₄ (M=Co, Fe, and/or V).

In some embodiments, the cathode comprises Li_(x)Mn₂O₄ (0<x<2) and/orLi_(x)MPO₄ (M=Mn, Fe, and/or V). In some embodiments, the cathodecomprises sulfur.

Other variations of the invention provide a battery structurecomprising:

(a) an anode for extracting selected metal ions;

(b) an assisted cathode comprising (i) a non-porous layer for insertingthe metal ions, and (ii) an oxidant capable of reacting with the metalions derived from the non-porous layer, to form a reductant; and

(c) an electrolyte for transporting the metal ions between the anode andthe assisted cathode,

wherein the non-porous layer is electronically conductive and permeableto the metal ions but not appreciably permeable to any other chemicalspecies.

In certain embodiments of this variation, the ionic conductivity of themetal ions in the non-porous layer is selected from about 10⁻⁵ to 10⁻²S/cm and the electronic conductivity of electrons in the non-porouslayer is selected from about 10⁻² to 10² S/cm. For example, the ionicconductivity of the metal ions may be selected from about 10⁻³ to 10⁻²S/cm and the electronic conductivity may be selected from about 10⁻¹ to1 S/cm.

The selected metal ions are lithium ions and the non-porous layercomprises lithium metal oxide, in some embodiments. In variousembodiments, the non-porous layer comprises one or more compositionsselected from the group consisting of Li_(x)Mn₂O₄ (0<x<2), Li_(x)CoO₂(0<x<1), Li_(x)NiO₂ (0<x<1), Li_(x)V₂O_(y) (0<x<5, 4<y<5), Li_(x)TiO₂(0<x<1), Li_(4+x)Ti₅O₁₂ (0<x<3), Li_(x)WO₃ (0<x<0.5), Li_(x)Nb₂O₅(0<x<3), Li_(x)TiS₂ (0<x<1), Li_(x)MPO₄ (M=Mn, Fe, and/or V; 0<x<1), andLiMPO₄ (M=Co, Fe, and/or V).

In some embodiments utilizing an assisted cathode, the oxidant comprisesLi₂S_(y), y=2-8. In other embodiments, the oxidant is selected from thegroup consisting of O₂, Br₂, SO₂, SOCl₂, SO₂Cl₂, and I₂. Optionally,when O₂ is used as an oxidant, the oxygen is derived from air.

This invention provides a lithium-ion battery comprising a plurality ofbattery structures, each including:

(a) an anode for extracting lithium ions;

(b) a cathode for inserting lithium ions;

(c) an electrolyte for transporting lithium ions between the anode andthe cathode; and

(d) a separator comprising a non-porous layer that is electronicallyconductive and permeable to lithium ions but not appreciably permeableto any other chemical species.

This invention further provides a lithium-sulfur battery comprising aplurality of battery structures, each including:

(a) an anode for extracting lithium ions;

(b) an assisted cathode comprising (i) a non-porous layer for insertingthe lithium ions, and (ii) polysulfides of lithium as oxidants capableof reacting with the lithium ions derived from the non-porous layer; and

(c) an electrolyte for transporting the lithium ions between the anodeand the assisted cathode,

wherein the non-porous layer is electronically conductive and permeableto the metal ions but not appreciably permeable to any other chemicalspecies.

This invention additionally provides a lithium-air battery comprising aplurality of battery structures, each including:

(a) an anode for extracting lithium ions;

(b) an assisted cathode comprising (i) a non-porous layer for insertingthe lithium ions, and (ii) O₂ derived from air as an oxidant capable ofreacting with the lithium ions derived from the non-porous layer; and

(c) an electrolyte for transporting the lithium ions between the anodeand the assisted cathode,

wherein the non-porous layer is electronically conductive and permeableto the metal ions but not appreciably permeable to any other chemicalspecies.

In a particular embodiment, a lithium-based battery comprising aplurality of electrochemical cells is provided, wherein each of thecells includes:

(a) an anode for extracting lithium ions;

(b) a cathode for inserting the lithium ions;

(c) an electrolyte for transporting the lithium ions between the anodeand the cathode; and

(d) a free-standing separator comprising a laminated non-porous layerthat is permeable to the lithium ions but not appreciably permeable toany other chemical species,

wherein the non-porous layer comprises one or more compositions selectedfrom the group consisting of Li_(x)Mn₂O₄ (0<x<2), Li_(x)CoO₂ (0<x<1),Li_(x)NiO₂ (0<x<1), Li_(x)V₂O_(y) (0<x<5, 4<y<5), Li_(x)TiO₂ (0<x<1),Li_(4+x)Ti₅O₁₂ (0<x<3), Li_(x)WO₃ (0<x<0.5), Li_(x)Nb₂O₅ (0<x<3),Li_(x)TiS₂ (0<x<1), Li_(x)MPO₄ (M=Mn, Fe, and/or V; 0<x<1), and LiMPO₄(M=Co, Fe, and/or V);

and wherein the ionic conductivity of the metal ions in the non-porouslayer is from 10⁻³ to 10⁻² S/cm and the electronic conductivity ofelectrons in the non-porous layer is from 10⁻¹ to 1 S/cm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a lithium-sulfur battery with a lithium metal oxide layeras part of the separator, according to some embodiments of theinvention.

FIG. 2 depicts a lithium-ion battery employing non-porous lithium metaloxide as the battery separator, according to some embodiments.

FIG. 3 depicts a lithium-air battery that includes an aqueous solutionfor oxygen reduction at the cathode, according to some embodiments.

FIG. 4 illustrates a generalized scheme of various embodiments of theinvention, wherein the battery reaction utilizes an oxidant capable ofreacting with lithium metal oxide to form a reductant.

FIG. 5 depicts a lithium-ion battery with a non-porous lithium metaloxide layer on the cathode side, at which lithium polysulfide can reactwith lithium metal oxide to consume lithium and reduce polysulfide,according to some embodiments.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The structures and methods of the present invention will be described indetail by reference to various non-limiting embodiments of theinvention.

Unless otherwise indicated, all numbers expressing dimensions,capacities, conductivities, and so forth used in the specification andclaims are to be understood as being modified in all instances by theterm “about.” Without limiting the application of the doctrine ofequivalents to the scope of the claims, each numerical parameter shouldat least be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contextclearly indicates otherwise.

As used herein, “battery,” “battery structure,” “electrochemical cell,”“galvanic cell,” and the like are used interchangeably to mean one ormore unit cells to convert chemical energy into electrical energy.

The primary functional components of a typical battery are the anode;cathode; electrolyte, in which ions move between the anode and cathodein the electrolyte; and a separator between cathode and anode to blockpassage of electrons (prevent short circuit). Current collectors,normally metal, are used to transport electrons at the cathode andanode. The active ions move from the anode to the cathode duringdischarge and from the cathode to the anode when charging.

Some variations of the invention are premised on the discovery that asubstantially non-porous layer is a beneficial component of a batteryseparator for lithium-based batteries. For present purposes and in thecontext of lithium-based battery systems, “substantially non-porous” or“non-porous” are intended to mean that the layer is permeable to lithiumions (Li⁺) but not appreciably permeable to any other chemical species.A “chemical species” means an atom, molecule, or particle comprising atleast one proton. In various embodiments, the lithium-ion conductivityof the substantially non-porous layer is from 10⁻⁵ to 10⁻² S/cm,preferably from 10⁻³ to 10⁻² S/cm.

Generally speaking, with respect to metals ions selected for aparticular battery (i.e., not necessarily lithium ions), a “non-porous”layer means that the layer is permeable to the selected metal ions butnot appreciably permeable to any other chemical species.

Of course, the non-porous layer should not contain large pores, such asan average pore size of greater than 1 micron. That is, pores should notbe available for chemical species to pass through the separator layerdirectly (i.e., by simple pore diffusion or convection). If there areminor structural defects in the separator layer introduced duringbattery manufacturing or operation, small amounts of other chemicalspecies can be expected to pass through the layer by convection throughthe defects.

A non-porous layer is also electronically conductive in addition toproviding good lithium-ion conductivity, in preferred embodiments of theinvention. In various embodiments, the electronic conductivity of thenon-porous layer is from 10⁻² to 10⁻² S/cm, such as from 10⁻¹ to 1 S/cm.

As will be appreciated by skilled artisans, the flexibility to selectelectronically conductive materials for the non-porous layer opens upclasses of materials that would not be preferred if electronicconductivity needed to be minimized. For example, anode and cathodematerials can be implemented as the non-porous layer. Known lithium ionconductors tend to have low conductivities (˜10⁻⁶ S/cm). The ionicconductivity of battery electrode materials can reach at least 10⁻³ S/cmdue to the orders-of-magnitude higher mobile lithium ion concentrationin the solid phase.

One advantage to high ion conductivity is that the non-porous layer doesnot need to be extremely thin. Rather, the non-porous layer can berelatively thick, allowing it to be structurally free-standing.“Free-standing” here means that the non-porous layer, a composite(laminated) layer, does not rely on either the anode or cathode forstructural support. In various embodiments, the thickness of thenon-porous layer is in the range of 2-200 μm, such as 20-100 μm.

Non-porous layer compositions include, but are by no means limited to,Li_(x)Mn₂O₄ (0<x<2), Li_(x)CoO₂ (0<x<1), Li_(x)NiO₂ (0<x<1),Li_(x)V₂O_(y) (0<x<5, 4<y<5), Li_(x)TiO₂ (0<x<1), Li_(4+x)Ti₅O₁₂(0<x<3), Li_(x)WO₃ (0<x<0.5), and Li_(x)Nb₂O₅ (0<x<3). In addition,non-oxide materials such as Li_(x)TiS₂ (0<x<1), Li_(x)MPO₄ (M=Mn, Fe,and/or V; 0<x<1), and LiMPO₄ (M=Co, Fe, and/or V) can be utilized.

Variations of the present invention will now be described, including byreference to the accompanying figures. The figures providerepresentative illustration of the invention and are not limiting intheir content. It will be understood by one of ordinary skill in the artthat the scope of the invention extends beyond the specific embodimentsdepicted. The principles and scope of the present invention are notlimited to lithium-based batteries.

Lithium-sulfur batteries have theoretical energy densities of 2500 Wh/kg(watt-hours per kilogram), in contrast to 560 Wh/kg for lithium-ionbatteries. Commercialization of lithium-sulfur batteries has beenhindered by technical difficulties. When sulfur electrode is discharged,it forms a series of polysulfides that are soluble in common batteryelectrolytes. The dissolved compounds can migrate to the lithiumelectrode, effectively creating an internal short mechanism with greatlyreduced energy efficiency. Metal lithium forms dendrites during repeatedcycling due to non-uniform dissolution and deposition. These dendritesare highly reactive with electrolytes and can even penetrate theseparator to create internal shorting. The non-porous layer provided bythe present invention, by allowing passage of lithium ions but no otherchemical species, can effectively shut down these internal shortingmechanisms.

FIG. 1 depicts a lithium-sulfur battery structure employing the newseparator concept. In a normal lithium-sulfur battery, a porous polymerseparator is sandwiched between lithium 110 and sulfur 150 electrodesand soaked with liquid electrolyte. In FIG. 1, the separator consists ofthree layers—lithium metal oxide (LMO) 130 as the middle layer,sandwiched by a porous material (e.g., polymer) in the outer layers 120,140. The lithium metal oxide layer 130 is non-porous, exclusivelyallowing lithium ions to pass.

The composition of the lithium metal oxide layer can be selected fromany battery anode or cathode materials. In some embodiments, thecomposition includes one or more of materials selected from the groupconsisting of Li_(x)Mn₂O₄ (0<x<2), Li_(x)CoO₂ (0<x<1), Li_(x)NiO₂(0<x<1), Li_(x)V₂O_(y) (0<x<5, 4<y<5), Li_(x)TiO₂ (0<x<1),Li_(4+x)Ti₅O₁₂ (0<x<3), Li_(x)WO₃ (0<x<0.5), Li_(x)Nb₂O₅ (0<x<3),Li_(x)TiS₂ (0<x<1), Li_(x)MPO₄ (M=Mn, Fe, and/or V; 0<x<1), and LiMPO₄(M=Co, Fe, and/or V).

The non-porous layer may be fabricated from a powder precursor, in someembodiments. The powder may be mixed with a polymer binder (such aspolyvinylidene fluoride, PVDF) dissolved in a suitable solvent. Theslurry may be cast into tapes. After drying, the tapes may behot-pressed at a temperature above the melting point of the polymer sothat porosity can be eliminated.

The non-porous layer may be further laminated with two porous layers toform a composite separator. These porous layers are preferablyelectronically resistive to help prevent an electrical short circuit.The porous layers may be fabricated from any material that is suitableas a normal separator layer known in the art. Examples include olefinpolymers (e.g., polyethylene or polypropylene), fluorine-containingpolymers, cellulose polymers (e.g., paper), polyimides, nylons, glassfibers, alumina fibers, and porous metal foils. The form of the porouslayer may be a non-woven fabric, a woven fabric, a microporous film, afoil, or another configuration that may be selected for its mechanicalstrength or other properties, or for cost reasons.

The principles of the present invention can also be applied to variouslithium-ion battery structures. FIG. 2 shows a lithium-ion batterystructure wherein a non-porous lithium metal oxide layer (LMO) 230 ispart of the battery separator. This battery includes an anode 210, athree-layer separator comprising a lithium metal oxide (LMO) non-porouslayer 230 sandwiched by porous layers 220 and 240, and a cathode 250denoted in FIG. 2 as LMO2. LMO2 250 may be fabricated from any knowncathode materials. In some preferred embodiments, LMO2 includes LiMPO₄(M=Co, Fe, or V) and/or LiMn₂O₄ (or other manganese-containingcompounds).

During battery storage and cycling, in particular at elevatedtemperatures, metal from LMO2 250 can dissolve in the batteryelectrolytes and, without the presence of LMO 230, would migrate to thelithium-ion anode 210 surface and lead to capacity loss. The LMO layer230 blocks such migration, thus extending the lithium-ion battery'slife.

Other variations of the invention relate to lithium-air batteries.Lithium-air batteries generally use porous cathodes to catalyze thereduction of oxygen. These batteries have a theoretical energy densityof 5220 Wh/kg and have significant potential because atmospheric air maybe utilized at low cost and high availability. A major technicalchallenge associated with lithium-air batteries known in the art is thechemical corrosion of lithium due to moisture from the ambientatmosphere.

The non-porous layer described herein is effective for separating thelithium electrode from the ambient atmosphere, thereby reducing theinfluence of moisture and extending the battery's life. When anon-porous lithium metal oxide layer is present, it is possible to paira non-aqueous reaction involving lithium with a reaction involvingoxygen. The lithium metal oxide layer prevents water from contaminatingthe left-hand side of the battery. A non-aqueous environment for lithiumis important because lithium reacts intensely with water, forminglithium hydroxide and flammable hydrogen.

FIG. 3 depicts an exemplary lithium-air battery structure with anaqueous solution for oxygen reduction. The lithium metal oxide layer 330allows water to be utilized as a solvent on the right-hand side, withreference to FIG. 3. Water is a preferred solvent in some embodimentsbecause oxygen reduction in aqueous media is faster than in non-aqueousmedia. Additionally, water can dissolve Li₂O to form LiOH. Thisconversion may prevent passivation of the cathode 350 surface andincrease battery power.

In one embodiment of a lithium-air battery structure, a porous carbonelectrode is supported with platinum or nickel oxide catalyst. Theaqueous solution is 1-5 M KOH. Oxygen reduction generates OW anions. Thenet battery reaction is: 4 Li+O₂+2 H₂O=4 LiOH.

In some embodiments, a non-aqueous solution is employed for oxygenreduction on the cathode side. When reacting oxygen with lithiated metaloxide and in the absence of water, oxygen can form lithium peroxide,Li₂O₂, which may be reversibly charged. In these embodiments, thelithium metal oxide separator layer prevents water from reachinglithium.

The possible composition and methods of fabrication for non-porous layer330 of FIG. 3 are similar to those described above with reference toFIG. 1, except that the redox potential of lithium insertion into thenon-porous layer 330 should be close to the redox potential of oxygenreduction, which is between 2-3 V versus Li. Amorphous vanadium oxide ispreferred, since its potential continuously varies with the insertion oflithium.

Other variations of the invention are premised on the realization that anon-porous lithium metal oxide layer may be used to assist the overallchemical reaction at the cathode side, as follows. The generalizedscheme shown in FIG. 4 illustrates that any oxidant (Ox) capable ofreacting with lithium metal oxide (LMO) 430 may be used for the batteryreaction to form the reductant (Red). The cathode may include any liquidor gas that is capable of reacting with lithium metal oxide 430 in acertain voltage range.

As used herein, an “assisted cathode” is a combination of a lithiummetal oxide layer and a cathode-side fluid. Any fluid (liquid or gas)that can react with lithium metal oxide may be used in the assistedcathode, since the LMO layer only allows the passage of lithium ions andelectrons, but nothing else. Exemplary cathode fluids include, but arenot limited to, O₂, Br₂, SO₂, SOCl₂, SO₂Cl₂, and I₂. Various inertdiluents may be present, such as N₂.

FIG. 5 depicts a lithium-ion battery that incorporates an assistedcathode. In this particular design, graphitic carbon 510 and lithiummetal oxide 530 form a battery structure wherein the non-porous lithiummetal oxide layer 530 assists the overall chemical reaction at thecathode side. On the back side of the oxide electrode (not exposed tothe electrolyte) is a solution of lithium polysulfide dissolved insulfolane. Lithium polysulfide reacts with the lithium metal oxide 530to consume lithium.

During battery discharge, lithium is removed from the carbon anode 510and inserted into the oxide electrode 530, causing its potential todrop. Li₂S₈ will react with the oxide once its potential drops below itsreduction potential. This process may continue until all Li₂S₈ isconsumed. During battery charging, the reverse process takes place. Thenet battery reaction is the reduction of the polysulfide, which can berepresented with the overall chemical reaction Li₂S₈+6 Li=4 Li₂S₂ wherethe Li is derived from the selected lithium metal oxide 530 material.The metal oxide layer 530 effectively serves as a reaction mediator.This battery structure prevents sulfur crossover and makes use oflong-cycling lithiated carbon as the anode 510. If desired, Li metal maybe used instead of Li_(x) C₆ as the anode 510.

The possible composition and methods of fabrication for this non-porouslayer are similar to those described above with reference to FIG. 1,except that the redox potential of lithium insertion into the lithiumoxide layer is preferably lower than that of lithium addition to Li₂S₈.The reason for this preference is so that during battery discharge,Li₂S₈ spontaneously reduces the lithium metal oxide by removingelectrons and lithium ions. The potential difference, however, should beas small as possible to minimize energy loss to heat (due to exothermicenthalpy of reaction).

The battery voltage is determined by the potential difference betweenLMO and Li_(x)C₆, not between Li₂S₈ and Li_(x)C₆. Since the polysulfidereactions (Li₂S₈→Li₂S₆→Li₂S₄→Li₂S₃→Li₂S₂) take place at an averagevoltage of 2.0 V, it is preferred that the selected LMO can bereversibly discharged to this region. More preferably, a cathodematerial with no clear plateau is employed since the voltagecontinuously decreases until the reaction with polysulfide commences.Some preferred embodiments employ amorphous vanadium oxide, such ascompositions according to Li_(x)V₂O_(y) (wherein 0<x<5, 4<y<5).

In some embodiments, a plurality (two or more) of non-porous layers areused in an overall structure. For example, a first non-porous layer(such as lithium metal oxide, but not so limited) may be used within acomposite separator layer, while a second non-porous layer is employedat the cathode side to assist the net cathode chemistry, i.e. serve as areaction mediator. The composition, thickness, and other physical orchemical properties of the first and second non-porous layers, or morelayers if desired, may be the same or different.

Battery structural features applicable to many variations of theinvention will now be further described, again without limiting theinvention's scope in any way.

The cathode material, or the non-porous layer material within anassisted cathode, preferably exhibits long cycle life and calendar life.The material may be, for example, a lithium metal oxide, phosphate, orsilicate. Exemplary cathode or non-porous layer materials suitable forthe present invention include, but are not limited to, LiMO₂ (M=Co, Ni,Mn, or combinations thereof); LiM₂O₄ (M=Mn, Ti, or combinationsthereof); LiMPO₄ (M=Fe, Mn, Co, or combinations thereof); andLiM_(x)M′_(2-x)O₄ (M, M′=Mn or Ni).

The cathode, or the non-porous layer within an assisted cathode, mayfurther comprise one or more conductive fillers to provide enhancedelectronic conductivity. Examples of conductive fillers include, but arenot limited to, conductive carbons, graphites, activated carbon fibers,non-activated carbon nanofibers, metal flakes, metal powders, metalfibers, carbon fabrics, metal mesh, and electrically conductivepolymers. The cathode or non-porous layer may also further compriseother additives such as, for example, alumina, silica, andtransition-metal chalcogenides.

The cathode, or the non-porous layer within an assisted cathode, mayalso comprise a binder. The choice of binder material may vary widely solong as it is inert with respect to the other materials in the cathode.Useful binders are those materials, usually polymeric, that allow forease of processing of battery electrode composites and are generallyknown to those skilled in the art of electrode fabrication. Examples ofuseful binders include, but are not limited to,polytetrafluoroethylenes, polyvinylidene fluorides,ethylene-propylene-diene rubbers, polyethylene oxides, acrylates,methacrylates, divinyl ethers, and the like.

The anode material preferably exhibits long cycle life and calendarlife. Exemplary anode materials suitable for the present inventioninclude, but are not limited to, carbon materials such as graphite,coke, soft carbons, and hard carbons; and metals such as Si, Al, Sn, oralloys thereof. Other exemplary anode materials include titanium oxides,germanium, copper/tin, and lithium compounds containing metal oxides,such as oxides of W, Fe, and Co. Anodes can also include fillers,binders, and current collectors.

In some embodiments, the anode material consists essentially ofgraphitic carbon or another electron-conducting carbon. Some examples ofelectron-conducting carbon include natural graphites, such as flakygraphite, plate-like graphite, and other types of graphite;high-temperature sintered carbon products obtained, for example, frompetroleum coke, coal coke, celluloses, saccharides, and mesophase pitch;artificial graphites, including pyrolytic graphite; carbon blacks, suchas acetylene black, furnace black, Ketjen black, channel black, lampblack, and thermal black; asphalt pitch, coal tar, active carbon,mesophase pitch, and polyacetylenes.

Current collectors collect electrical current generated and provide anefficient surface for attachment of the electrical contacts leading tothe external circuit. Current collectors may be made from any suitablematerials, such as (but not limited to) Al, Cu, or Ni. The currentcollectors may also be fabricated from alloys, such as stainless steel.

Physically, the current collectors may be thin foils, such as foils withthicknesses in the 5-50 μm range. Other configurations that may be usedfor the current collectors include metal meshes, metal nets, perforatedmetal, metallized plastic films, metal grids, expanded metal grids,metal wools, woven carbon fabrics, woven carbon meshes, non-woven carbonmeshes, and carbon felts.

Electrolytes generally include a solvent and a lithium salt (anion pluslithium cation). Examples of the solvent that can be used includeaprotic organic solvents, such as propylene carbonate, ethylenecarbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate,methyl ethyl carbonate, γ-butyrolactone, methyl formate, methyl acetate,1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane,dioxane, acetonitrile, nitromethane, ethyl monoglyme, phosphorictriesters, trimethoxymethane, dioxolane derivatives, sulfolane,3-methyl-2-oxazolidinone, propylene carbonate derivatives,tetrahydrofuran derivatives, ethyl ether, 1,3-propanesultone, N-methylacetamide, acetonitrile, acetals, ketals, sulfones, sulfolanes,aliphatic ethers, cyclic ethers, glymes, polyethers, phosphate esters,siloxanes, dioxolanes, and N-alkylpyrrolidones. Ethylene carbonate andpropylene carbonate are preferable. As is known in the art, other minorcomponents and impurities may be present in the electrolyte composition.

Lithium salts include, but are not limited to, LiClO₄, LiBF₄, LiPF₆,LiCF₃SO₃, LiCF₃CO₂, LiAsF₆, LiSbF₆, LiAlCl₄, LiCl, LiBr, and LiI, whichmay be used alone or as a mixture of two or more. LiBF₄ and LiPF₆ arepreferable, in some embodiments. The concentration of the salt is notparticularly limited, but preferably is about 0.1 to 5 mol/L of theelectrolytic solution.

A battery can be packaged into either prismatic format cells orcylindrical cells, for example. In the prismatic format, the stackedstructure is preferably sealed with a packaging material capable ofpreventing air and water contamination of the battery.

Lithium-ion, lithium-sulfur, or lithium-air batteries can be included ina battery pack, which includes a plurality of electrochemical cells thatare electrically connected in series and/or in parallel. These batterypacks come in many shapes, sizes, capacities, and power ratings,depending on the intended use of the battery pack. Battery packs willtypically include a thermal-management system.

Lithium-based batteries according to this invention are suitable foroperating across a variety of temperature ranges. Exemplary operationtemperatures may be from −50° C. to 80° C., such as for militaryapplications. For computers and related devices, as well as forelectric-vehicle applications, temperatures from −30° C. to 60° C. arepossible.

Practical applications for this invention include, but are not limitedto, aircraft, satellites, launch vehicles, electric cars, electricbikes, laptop computers, mobile phones, cameras, medical devices, andpower tools. As will be appreciated by a person of skill in this art,the present invention has significant commercial relevance. Battery lifeis often a critical factor in the marketplace, especially forcommercial, military, and aerospace applications (e.g., satellites). Thecurrent invention provides long-term benefits in battery safety, cost,and performance.

In this detailed description, reference has been made to multipleembodiments and to the accompanying drawings in which are shown by wayof illustration specific exemplary embodiments of the invention. Theseembodiments are described in sufficient detail to enable those skilledin the art to practice the invention, and it is to be understood thatmodifications to the various disclosed embodiments may be made by askilled artisan. This invention also incorporates routineexperimentation and optimization of the structures, systems, and methodsdescribed herein.

Where methods and steps described above indicate certain eventsoccurring in certain order, those of ordinary skill in the art willrecognize that the ordering of certain steps may be modified and thatsuch modifications are in accordance with the variations of theinvention. Additionally, certain steps may be performed concurrently ina parallel process when possible, as well as performed sequentially.

All publications, patents, and patent applications cited in thisspecification are herein incorporated by reference in their entirety asif each publication, patent, or patent application were specifically andindividually put forth herein.

The embodiments, variations, and figures described above should providean indication of the utility and versatility of the present invention.Other embodiments that do not provide all of the features and advantagesset forth herein may also be utilized, without departing from the spiritand scope of the present invention. Such modifications and variationsare considered to be within the scope of the invention defined by theclaims.

What is claimed is:
 1. A battery structure comprising: (a) an anode forextracting selected metal ions; (b) a separator comprising a firstnon-porous layer that is electronically conductive and permeable to saidmetal ions but not appreciably permeable to any other chemical species,wherein electronic conductivity of electrons in said first non-porouslayer is about 10⁻² S/cm or higher as measured within a temperaturerange from −50° C. to 80° C., and wherein said first non-porous layer islaminated with electronically resistive porous layers; (c) an assistedcathode comprising a second non-porous layer for inserting said metalions, wherein said second non-porous layer is electronically conductiveand permeable to said metal ions but not appreciably permeable to anyother chemical species; and (d) a liquid electrolyte for transportingsaid metal ions between said anode and said assisted cathode.
 2. Thebattery structure of claim 1, wherein the ionic conductivity of saidmetal ions in said first non-porous layer is selected from about 10⁻⁵ to10⁻² S/cm and the electronic conductivity of electrons in said firstnon-porous layer is selected from about 10⁻² to 10² S/cm, each of saidionic conductivity and said electronic conductivity as measured within atemperature range from −50° C. to 80° C.
 3. The battery structure ofclaim 2, wherein said ionic conductivity of said metal ions is selectedfrom about 10⁻³ to 10⁻² S/cm and said electronic conductivity isselected from about 10⁻¹ to 1 S/cm, each of said ionic conductivity andsaid electronic conductivity as measured within a temperature range from−50° C. to 80° C.
 4. The battery structure of claim 1, wherein saidselected metal ions are lithium ions and said first non-porous layercomprises lithium metal oxide.
 5. The battery structure of claim 1,wherein said first non-porous layer comprises one or more compositionsselected from the group consisting of Li_(x)Mn₂O₄ (0<x<2), Li_(x)CoO₂(0<x<1), Li_(x)NiO₂ (0<x<1), Li_(x)V₂O_(y) (0<x<5, 4<y<5), Li_(x)TiO₂(0<x<1), Li_(4+x)Ti₅O₁₂ (0<x<3), Li_(x)WO₃ (0<x<0.5), Li_(x)Nb₂O₅(0<x<3), Li_(x)TiS₂ (0<x<1), Li_(x)MPO₄ (M=Mn, Fe, and/or V; 0<x<1), andLiMPO₄ (M=Co, Fe, and/or V).
 6. The battery structure of claim 1,wherein an oxidant reacts at said assisted cathode with said metal ionsto form a reductant, and wherein said oxidant comprises Li₂S_(y), y=2-8.7. The battery structure of claim 1, wherein at said assisted cathode,an oxidant reacts with said metal ions to form a reductant, and whereinsaid oxidant is selected from the group consisting of O₂, Br₂, SO₂,SOCl₂, SO₂Cl₂, and I₂.
 8. The battery structure of claim 7, wherein saidoxidant is O₂ derived from air.
 9. A lithium-ion battery comprising aplurality of battery structures each provided in accordance with claim1, wherein said selected metal ions are lithium ions.
 10. Alithium-sulfur battery comprising a plurality of battery structures eachprovided in accordance with claim 1, wherein said selected metal ionsare lithium ions, wherein an oxidant reacts at said assisted cathodewith said metal ions to form a reductant, and wherein said oxidantcomprises polysulfides of lithium.
 11. A lithium-air battery comprisinga plurality of battery structures each provided in accordance with claim1, wherein said selected metal ions are lithium ions, wherein at saidassisted cathode, an oxidant reacts with said metal ions to form areductant, and wherein said oxidant is O₂ derived from air.
 12. Thebattery structure of claim 1, wherein said first non-porous layercomprises a composition consisting of Li_(x)Mn₂O₄ (0<x<2).